Vacuum sewer systems are commonly used on large vessels, such as, for example, cruise ships. In recent times, vacuum sewer systems have been used for municipal sewer systems. As illustrated, for example, in U.S. Pat. No. 5,588,458 to Ushitora et al., a typical sewer system includes a vacuum pit, or a soiled water basin, that collects soiled water from a plurality of sources, e.g., in a residential setting, one soiled water basin may be used to accept soiled water from more than one house. Soiled water stored in the soiled water basin may be sucked through a suction pipe by opening a vacuum valve. The system may include a vacuum valve controller that closes the vacuum valve by detecting that the suction pipe has begun to suck air from a change of the pressure difference between two points in the suction pipe. These two points are illustrated as being different in height along the suction pipe from one another. Accordingly, the vacuum sewer system disclosed in the Ushitora et al. '548 patent is adapted to sense the level of soiled water in the soiled water basin using pressure differential to close a vacuum valve.
Another type of vacuum sewer system is disclosed in U.S. Pat. No. 4,034,421 to Pihl et al. and includes a tank provided for the collection of liquid-mixed wastes and a circulating pump having an inlet and outlet connected to the tank. The circulating pump is adapted to circulate the tank contents in a closed path for agitation and aeration. A liquid jet pump is inserted in the closed path to establish the necessary vacuum for the sewer system.
One problem that arises in typical vacuum sewer systems, however, is the case where there is a malfunction in the valve connecting the suction pipe to the vacuum pit, i.e., the vacuum sewer valve. A vacuum sewer valve that is stuck in an opened position, for example, may cause a decrease in efficiency of the vacuum sewer system. More particularly, the vacuum sewer system relies on the ability to apply a predetermined amount of vacuum pressure to each of the vacuum pits. A vacuum sewer valve that is stuck open on one vacuum pit, or even partially opened, may cause performance degradation of the suction able to be applied to the remaining pits, thereby decreasing the efficiency of the vacuum sewer system as a whole. Decreased efficiency of such a system may lead to increased energy consumption.
As described above, a typical vacuum sewer system may service a wide area. In that wide area, a single vacuum sewer system may have a plurality of spaced apart vacuum pits connected to a vacuum station, and each vacuum pit may be adapted to receive soiled water from a plurality of residential structures. Accordingly, if one vacuum sewer valve on one vacuum pit malfunctions, there currently exists no efficient manner to pinpoint the location of the vacuum pit where the valve may be malfunctioning. One manual method that is known for locating a malfunctioning vacuum sewer valve in a vacuum sewer system is for maintenance crews to drive to each vacuum pit and listen to hear if suction that is continuously running, which may be an indication that the vacuum sewer valve is stuck in the open position. This manual method, however, requires the use of many man hours, as well as the consumption of fuel to power the vehicle that is to transport the maintenance crew.
There exists a need for a system that provides an indication that a valve in a vacuum suction system is malfunctioning, as well as providing an indication of the location of the malfunctioning valve.